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Date:   Thu, 8 Dec 2022 10:45:18 -0800
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Subject: Re: [PATCH v3 0/5] cpumask: improve on cpumask_local_spread()
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To:     Yury Norov <yury.norov@gmail.com>, <linux-kernel@vger.kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Barry Song <baohua@kernel.org>,
        "Ben Segall" <bsegall@google.com>,
        haniel Bristot de Oliveira <bristot@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        "Gal Pressman" <gal@nvidia.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Heiko Carstens <hca@linux.ibm.com>,
        Ingo Molnar <mingo@redhat.com>,
        "Jakub Kicinski" <kuba@kernel.org>,
        Jason Gunthorpe <jgg@nvidia.com>,
        "Jesse Brandeburg" <jesse.brandeburg@intel.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        "Leon Romanovsky" <leonro@nvidia.com>,
        Mel Gorman <mgorman@suse.de>,
        "Peter Zijlstra" <peterz@infradead.org>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Saeed Mahameed <saeedm@nvidia.com>,
        "Steven Rostedt" <rostedt@goodmis.org>,
        Tariq Toukan <tariqt@nvidia.com>,
        "Tariq Toukan" <ttoukan.linux@gmail.com>,
        Tony Luck <tony.luck@intel.com>,
        "Valentin Schneider" <vschneid@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>
CC:     <linux-crypto@vger.kernel.org>, <netdev@vger.kernel.org>,
        <linux-rdma@vger.kernel.org>
References: <20221208183101.1162006-1-yury.norov@gmail.com>
From:   Jacob Keller <jacob.e.keller@intel.com>
In-Reply-To: <20221208183101.1162006-1-yury.norov@gmail.com>
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On 12/8/2022 10:30 AM, Yury Norov wrote:
> cpumask_local_spread() currently checks local node for presence of i'th
> CPU, and then if it finds nothing makes a flat search among all non-local
> CPUs. We can do it better by checking CPUs per NUMA hops.
> 
> This series is inspired by Tariq Toukan and Valentin Schneider's
> "net/mlx5e: Improve remote NUMA preferences used for the IRQ affinity
> hints"
> 
> https://patchwork.kernel.org/project/netdevbpf/patch/20220728191203.4055-3-tariqt@nvidia.com/
> 
> According to their measurements, for mlx5e:
> 
>          Bottleneck in RX side is released, reached linerate (~1.8x speedup).
>          ~30% less cpu util on TX.
> 
> This patch makes cpumask_local_spread() traversing CPUs based on NUMA
> distance, just as well, and I expect comparable improvement for its
> users, as in case of mlx5e.
> 
> I tested new behavior on my VM with the following NUMA configuration:
> 
> root@debian:~# numactl -H
> available: 4 nodes (0-3)
> node 0 cpus: 0 1 2 3
> node 0 size: 3869 MB
> node 0 free: 3740 MB
> node 1 cpus: 4 5
> node 1 size: 1969 MB
> node 1 free: 1937 MB
> node 2 cpus: 6 7
> node 2 size: 1967 MB
> node 2 free: 1873 MB
> node 3 cpus: 8 9 10 11 12 13 14 15
> node 3 size: 7842 MB
> node 3 free: 7723 MB
> node distances:
> node   0   1   2   3
>    0:  10  50  30  70
>    1:  50  10  70  30
>    2:  30  70  10  50
>    3:  70  30  50  10
> 
> And the cpumask_local_spread() for each node and offset traversing looks
> like this:
> 
> node 0:   0   1   2   3   6   7   4   5   8   9  10  11  12  13  14  15
> node 1:   4   5   8   9  10  11  12  13  14  15   0   1   2   3   6   7
> node 2:   6   7   0   1   2   3   8   9  10  11  12  13  14  15   4   5
> node 3:   8   9  10  11  12  13  14  15   4   5   6   7   0   1   2   3
> 
> v1: https://lore.kernel.org/lkml/20221111040027.621646-5-yury.norov@gmail.com/T/
> v2: https://lore.kernel.org/all/20221112190946.728270-3-yury.norov@gmail.com/T/
> v3:
>   - fix typo in find_nth_and_andnot_bit();
>   - add 5th patch that simplifies cpumask_local_spread();
>   - address various coding style nits.
> 

The whole series look reasonable to me!

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>